Device for measuring currents in a high voltage conductor by modulated radiated beams

ABSTRACT

A modulation device at a high voltage has a reflector for reflecting high frequency oscillations in accordance with the magnitude of the current to be measured. The reflector has resonant characteristics corresponding to the magnitude of the current to be measured. A transmitter transmits high frequency oscillations to the reflector. A receiver converts the reflected oscillations to signals corresponding to the magnitude of the current to be measured.

United States Patent Hermstein et al. July 4, 1972 [54]glltvlgEGliloRoMEAzURlNG CURRENTS [56] References Cited A I V LTAECONDUCTOR BY MODULATED RADIATED BEAMS UNITED STATES PATENTS 3,506,8334/1970 Von Willisen ..250/199 [721 hvenmrs' 32: 1? l 'g 3,569,835 3/1971l-larner ..340 207x many 3,335,367 8/1967 Skooglund mt. ..324/96 [73]Assignee: Siemens Aktiengesells'chaft, Berlin, Ger- 3,l59,80l l2/l964Wiedemann ..332/30 V many Primary ExaminerGerard H. Strecker [22] Flled'1970 Attorney-Curt M. Avery, Arthur E. Wilfond, Herbert L. [211 App].No.: 61,064 Lernerand Daniel.l.Tick

[30] Foreign Application Priority Data [57] ABSTRACT Aug 6 1969 GermanyP19 40 614 5 A modulation device at a high voltage has a reflector forreflecting high frequency oscillations in accordance with the 52 0.8.0..324/96 magnitude the Current be measured- The reflect 51 int. Cl..G0lr 19/00, G0lr3l/00 resonant characteristics P" the magnitude 0f 58Field of Search ..324/96, 127,585 B, 58.5 c; the current to be measured-A transmitter transmits high frequency oscillations to the reflector. Areceiver converts the reflected oscillations to signals corresponding tothe magnitude of the current to be measured.

9 Claims, 4 Drawing Figures I HIGH vomrsr CONDUCTOR H MODULATION DEV/CEM REFL ECTED I OSCILIAT/OIVS Ur1-l I mum!) I 05CILLATION$ UrZ f l\\ l\REFLECTOR RI I UHF USCILLA TIOIVS A TRANSMITTER CAPACITANCE 0100f KdRESONANT CIREU/T SK FREmcr/o/v DEV/CE RE I REFLECTOR R2 DEVICE FORMEASURING CURRENTS IN A HIGH VOLTAGE CONDUCTOR BY MODULATED RADIATEDBEAMS DESCRIPTION OF THE INVENTION The invention relates to a device formeasuring currents in a high voltage conductor. More particularly, theinvention relates to a device for measuring currents in a high voltageconductor and for transmitting the measured values from a high voltageside of the device to a low voltage side of the device. Oscillations aremodulated at a high frequency in a modulating device at the high voltageside of the device.

In a known current measuring device of the type of the invention,linearly polarized microwave beams are transmitted to a waveguide via aferrite rod, which rotates the plane of polarization of the microwavesin accordance with the magnitude of the current to be measured in thehigh voltage conductor. The modulated microwaves are subsequentlyreflected to the low voltage side of the device, where they aredemodulated and converted into a measurement magnitude or signalproportional to the magnitude of the current to be measured in the highvoltage conductor.

The principal object of the invention is to provide a new and improveddevice for measuring currents in a high voltage conductor.

An object of the invention is to provide a device for measuring currentsin a high voltage conductor, which device utilizes only passive circuitcomponents as a reflector at the high voltage side of the device, sothat operating voltages are not required at the high voltage side todetermine the measured magnitudes, and the output required for operatingthe device is low and the maintenance and servicing of the device areconsiderably simplified.

An object of the invention is to provide a device for measuring currentsin a high voltage conductor, which device need not have insulated orencapsulated transmission paths for protection from the free atmosphere,and may therefore be utilized in the open air.

An object of the invention is to provide a device for measuring currentsin a high voltage conductor, which device functions with efficiency,effectiveness and reliability.

In accordance with the invention, a device for measuring currents in ahigh voltage conductor and for transmitting the measured values from ahigh voltage side of the device to a low voltage side of the devicecomprises a modulation device at the high voltage side of the device.The modulation device has reflector means for reflecting high frequencyoscillations in accordance with the magnitude of the current to bemeasured. The reflector means has resonant characteristics cor--responding to the magnitude of the current to be measured. A transmittertransmits high frequency oscillations to the reflector means of themodulation device. A receiver converts the oscillations reflected by thereflector means of the modulation device to signals corresponding to themagnitude of the current to be measured.

A high voltage conductor conducts the current to be measured. Thereflector means of the modulation device comprises a resonant circuitcoupled to the high voltage conductor and has a resonant frequency whichvaries in accordance with the magnitude of the current to be measured,and a reflector connected to the resonant circuit.

The resonant circuit of the reflector means of the modulation deviceincludes a capacitance diode having a capacitance which varies inaccordance with the magnitude of the current to be measured therebyvarying the resonant frequency of the resonant circuit in accordancewith the magnitude of the current to be measured. Rectifier meanscouples the capacitance diode of the resonant circuit of the reflectormeans of the modulation device to the high voltage conductor therebycoupling the capacitance diode to a voltage proportional to the currentto be measured.

A saturation converter energized by the current to be measured may beutilized to provide a constant auxiliary voltage for determining theworking point of the capacitance diode of the resonant circuit.

The transmitter may comprise a warble transmitter at the low voltageside of the device having a sampling frequency determined by the desiredaccuracy of measurement.

The transmitter transmits high frequency oscillations having a fixedfrequency and the reflector means of the modulation device reflects thehigh frequency oscillations received from the transmitter as a mainradiation having the fixed frequency and as a sideband radiation havinga frequency corresponding to the current to be measured.

The high frequency oscillations may be transmitted by the transmitterdirectly and unmodulated to the receiver and the receiver demodulatesthe oscillations reflected by the reflector means of the modulationdevice by mixing with the oscillations directly transmitted thereto fromthe transmitter.

The high frequency oscillations transmitted and reflected in the currentmeasuring device of the invention are in the decirneter, centimeter andmillimeter range. The reflector means may be designed in various ways.As hereinbefore described, the reflector means preferably comprises areflec-. tor having an electrical oscillating or resonant circuitelectrically connected thereto, the resonant frequency of which circuitvaries in accordance with the current to be measured. The variation inthe resonant frequency of the resonant or oscillating circuit, inaccordance with the current to be measured, is preferably effected by acapacitance diode which varies in capacitance in accordance with thecurrent to be measured. The capacitance diode of the resonant circuit iscoupled to a voltage proportional to the current to be measured via, forexample, a diode. Since, however, only one half-wave of an alternatingcurrent to be measured may be evaluated when a single diode is utilized,two oscillating or resonant circuits may be connected in series with thereflector in order to provide a complete measurement of an alternatingcurrent. This results in a high expenditure. It is therefore preferableto connect the capacitance diode to the voltage proportional to thecurrent to be measured via a double path rectifier circuit. This permitsboth half-waves of an alternating current to be measured in a relativelysimple manner.

The reflector means of the current measuring device of the inventionrequires no auxiliary voltage. If a particularly large working area isto be measured with great accuracy, however, particularly including lowinstantaneous magnitudes of the current to be measured, an auxiliaryvoltage may be utilized to appropriately place the working point of thecapacitance diode. The auxiliary voltage is preferably provided by asaturation converter which is energized or excited by the current to bemeasured.

As hereinbefore described, the transmitter preferably comprises a warbletransmitter at the low voltage side of the device having a samplingfrequency which is determined by the desired accuracy of measurement.The frequency of the high frequency oscillations transmitted by thewarble transmitter and reflected by the reflector means preferably isthe resonant frequency of the reflector means, since the resonantfrequency of the reflector means varies in accordance with the magnitudeof the current to be measured. The receiver may thus include ademodulator which produces a measured magnitude or signal correspondingto the magnitude of the current to be measured, from the reflectedfrequency spectrum.

In the current measuring device, as hereinbefore described, wherein thetransmitter transmits high frequency oscillations having a fixedfrequency and the reflector means of the modulation device reflects thehigh frequency oscillations received from the transmitter as a mainradiation having the fixed frequency and as a sideband radiation'havinga frequency corresponding to the current to be measured, only thesideband radiation is demodulated from the reflected frequency spectrumat the receiver. When the high frequency oscillations transmitted by thetransmitter are also directly transmitted to the receiver, ashereinbefore described, the demodulation in the receiver is facilitatedby any suitable demodulating process which utilizes such directlytransmitted oscillations such as, for example, mixing or compensating.

In order that the invention may be readily carried into effect, it willnow be described with reference to the accompanying drawing, wherein:

FIG. 1 is a schematic block diagram of an embodiment of the device ofthe invention for measuring currents in a high voltage conductor;

FIG. 2 is a schematic block diagram of an embodiment of the reflectiondevice of the modulation device of the device of the invention formeasuring currents in a high voltage conductor;

FIG. 3 is a schematic diagram of another embodiment of the device of theinvention for measuring currents in a high voltage conductor; and

FIG. 4 is a modification of the embodiment of FIG. 2.

In FIG. 1, a transmitter S is provided at the low voltage side of thedevice and transmits, for example, UHF oscillations Usl to a modulationdevice M connected in a high voltage conductor H. A current I flowsthrough the high voltage conductor H and is the current to be measured.

The current I charges the modulation device M and controls the operationof a reflector R1 of said modulation device in accordance with thereflection characteristics of said reflector. Consequently, the UHFoscillations Usl are modulated by the reflector R1 and the reflectedmodulated oscillations Url are reflected from said reflector to the lowvoltage side of the device and are received by a receiver E. Thereceiver E converts the reflected modulated oscillations Url to measuredmagnitudes of signals corresponding to the magnitude of the current I tobe measured in the high voltage conductor H.

The reflection device or reflector means RE, are shown in FIG. 2,comprises an antenna which functions as a reflector R2. The reflector R2is electrically connected to an oscillating or resonant circuit SK. Theoscillating or resonant circuit SK comprises a winding Sp and acapacitance diode Kd Kd connected in parallel with each other. Avoltage. u is derived from a current i proportional to the current to bemeasured and is applied to the oscillating circuit SK via a diode D. Thevoltage u is derived from a resistor W through which the current ito bemeasured flows or a current proportional to this current.

The capacitance of the capacitance diode Kd of the resonant circuit SKvaries in accordance with the magnitude of the current i to be measuredor of the voltage u derived from said current. When the capacitance ofthe capacitance diode Kd Kd varies, the resonant frequency of theresonant circuit SK varies accordingly. The reflection operation of thereflection device RE varies in accordance with the variation of theresonant frequency of the resonant circuit SK.

A transmitter (not shown in FIG. 2) such as, for example, a warbletransmitter, transmits UHF oscillations Us2 to the reflection device RE.The UHF oscillations Usare reflected by the reflection device RE asreflected oscillations Ur2, at a frequency which coincides with theresonant frequency of the resonant circuit SK. The UHF oscillations Us2are modulated at a frequency which varies in accordance with thefrequency of oscillation of the resonant circuit SK, which in turn, ashereinbefore described, varies in accordance with the magnitude of thecurrent i to be measured.

The reflected oscillations Ur2 are received by a receiver (not shown inFIG. 2) which converts said reflected oscillations into measuringmagnitudes or signals corresponding to the magnitude of the current i tobe measured. The particularly prevalent frequency in the frequencyspectrum reflected by the reflection device RE is a measure of thecurrent i to be measured and is converted in the receiver to themeasuring magnitude or signal. The measuring magnitude or signal, whichcorresponds to the magnitude of the current i to be measured, isprovided at an output tenninal A of the receiver (FIG. 1).

The accuracy of the measurement results of the current measuring deviceof the invention, utilizing the reflection device RE of FIG. 2,primarily depends upon the sampling frequency of the warble transmitter.The higher the sampling frequency, the better, and the more precise thedetennination of the measuring magnitude or signal.

FIG. 3 is another embodiment of the device of the invention formeasuring currents in a high voltage conductor. In the embodiment ofFIG. 3, a transmitter S1 is connected in series with a semiconductivereflector Sp l. The semiconductive reflector Spl reflects oscillationsUs3l from the transmitter S1 to another reflector Sp2. The reflector Sp2reflects the oscillations to a mixer or mixing stage Mi. Anotherportion, Us32, of the oscillations issued by the transmitter S1, isdirected to a modulation device Ml, arranged at the high voltage side ofthe device.

The modulation device M1 is charged with current II in a high voltageconductor Hi. This causes the reflection characteristics of a reflectorR3 of the modulation device Ml to be influenced. The oscillations Us32are reflected as modulated oscillations Ur3 from the reflector R3 to thelow voltage side of the device and delivered to the mixing stage Mi. Themixing stage Mi is connected to a demodulator Dm via an amplifier. Thedemodulation Dm derives the side band radiation, or beam, in thereflected frequency spectrum.

FIG. 4 is a modification of the embodiment of FIG. 2. FIG. 4 illustrateshow the reflection device, which includes the capacitance diode, asillustrated in FIG. 2, may be supplied with a constant auxiliaryvoltage. The constant auxiliary voltage may assist in establishing theworking point of the capacitance diode. The same components of FIGS. 2and 4 are identified by the same reference numerals.

A current which is proportional to the current i, to be measured, flowsthrough the primary winding wl of a saturation transformer S.W. Thesecondary winding w2 of the saturation transformer SW, is connected to arectifier G. The rectifier G is connected in series with a capacitor C.The capacitor C is connected to the capacitance diode Kd via a resistorWil and a resistor Wi2, preferably via an intermediary connection of acircuit device which functions as a voltage limiter Sb.

The current measuring device of the invention has the advantage that,since only passive circuit components are utilized in the reflectiondevice RE, no operating voltage are required at the high voltage side ofthe device for determining the measured magnitudes. This requires arelatively low output for operating the current measuring device of theinvention and considerably simplifies the maintenance and servicing ofsaid current measuring device.

Another advantage of the current measuring device of the invention isthat the transmitter channels from the low voltage to the high voltageside and vice versa need not be encapsulated or insulated against thefree atmosphere, since the high frequency oscillations are not impededby either vapor or fog. This advantage is of particular importance whenthe current measuring device of the invention is operated in the openair While the invention has been described by means of a specificexample and in a specific embodiment, we do not wish to be limitedthereto, for obvious modifications will occur to those skilled in theart without departing from the spirit and scope of the invention.

We claim:

1. A device for measuring currents in a high voltage conductor and fortransmitting the measured values from a high voltage side of the deviceto a low voltage side of the device, said device comprising a modulationdevice at the high voltage side of the device,

said modulation device having reflector means for reflecting highfrequency oscillations in accordance with the magnitude of the currentto be measured, said reflector means having resonant characteristicscorresponding to the magnitude of the current to be measured;

transmitting means at the low voltage side for transmitting highfrequency oscillations to the reflector means of said modulation device,said transmitting means having a frequency range and said reflectormeans having a resonant frequency which varies within the same frequencyrange as the transmitting means; and

receiving means at the low voltage side for converting the oscillationsreflected by the reflector means of said modulation device to signalscorresponding to the magnitude of the current to be measured.

2. A device as claimed in claim 1, further comprising a high voltageconductor conducting the current to be measured, and wherein thereflector means of said modulation device comprises a resonant circuitcoupled to said high voltage conductor and having a resonant frequencywhich varies in accordance with the magnitude of the current to bemeasured, and a reflector connected to said resonant circuit.

3. A device as claimed in claim 1, wherein said transmitting meanscomprises a warble transmitter at the low voltage side of the device andhaving a sampling frequency determined by the desired accuracy ofmeasurement.

4. A device as claimed in claim 1, wherein said transmitting meanstransmits high frequency oscillations having a fixed frequency and thereflector means of said modulation device reflects the high frequencyoscillations received from said transmitting means as a main radiationhaving the fixed frequency and as a sideband radiation having afrequency corresponding to the current to be measured.

5. A device as claimed in claim 1, further comprising means fortransmitting the high frequency oscillations transmitted by saidtransmitting means directly and unmodulated to said receiving means andwherein said receiving means demodulates the oscillations reflected bythe reflector means of said modulation device by mixing with theoscillations directly transmitted thereto from said transmitting means.

6. A device as claimed in claim 2, wherein the resonant circuit of thereflector means of said modulation device includes a capacitance diodehaving a capacitance which varies in accordance with the magnitude ofthe current to be measured thereby varying the resonant frequency of theresonant circuit in accordance with the magnitude of the current to bemeasured.

7. A device as claimed in claim 6, further comprising rectifier meanscoupling the capacitance diode of the resonant circuit of the reflectormeans of said modulation device to said high voltage conductor therebycoupling said capacitance diode to a voltage proportional to the currentto be measured.

8. A device as claimed in claim 7, further comprising saturationconverting means energized by the current to be measured for providing aconstant auxiliary voltage for detennining the working point of thecapacitance diode of said resonant circuit.

9. A device as claimed in claim 1, wherein of the high frequencyoscillations transmitted by the transmitting means, the reflector meansreflects that frequency which corresponds to the resonant frequency ofsaid reflector means whereby the reflector means reflects the frequencycorresponding to a specific magnitude of the current to be measuredsince the resonant frequency of the reflector means varies in accordancewith the current to be measured.

1. A device for measuring currents in a high voltage conductor and fortransmitting the measured values from a high voltage side of the deviceto a low voltage side of the device, said device comprising a modulationdevice at the high voltage side of the device, said modulation devicehaving reflector means for reflecting high frequency oscillations inaccordance with the magnitude of the current to be measured, saidreflector means having resonant characteristics corresponding to themagnitude of the current to be measured; transmitting means at the lowvoltage side for transmitting high frequency oscillations to thereflector means of said modulation device, said transmitting meanshaving a frequency range and said reflector means having a resonantfrequency which varies within the same frequency range as thetransmitting means; and receiving means at the low voltage side forconverting the oscillations reflected by the reflector means of saidmodulation device to signals corresponding to the magnitude of thecurrent to be measured.
 2. A device as claimed in claim 1, furthercomprising a high voltage conductor conducting the current to bemeasured, and wherein the reflector means of said modulation devicecomprises a resonant circuit coupled to said high voltage conductor andhaving a resonant frequency which varies in accordance with themagnitude of the current to be measured, and a reflector connected tosaid resonant circuit.
 3. A device as claimed in claim 1, wherein saidtransmitting means comprises a warble transmitter at the low voltageside of the device and having a sampling frequency determined by thedesired accuracy of measurement.
 4. A device as claimed in claim 1,wherein said transmitting means transmits high frequency oscillationshaving a fixed frequency and the reflector means of said modulationdevice reflects the high frequency oscillations received from saidtransmitting means as a main radiation having the fixed frequency and asa sideband radiation having a frequency corresponding to the current tobe measured.
 5. A device as claimed in claim 1, further comprising meansfor transmitting the high frequency oscillations transmitted by saidtransmitting means directly and unmodulated to said receiving means andwherein said receiving means demodulates the oscillations reflected bythe reflector means of said modulation device by mixing with theoscillations directly transmitted thereto from said transmitting means.6. A device as claimed in claim 2, wherein the resonant circuit of thereflector means of said modulation device includes a capacitance diodehaving a capacitance which varies in accordance with the magnitude ofthe current to be measured thereby varying the resonant frequency of theresonant circuit in accOrdance with the magnitude of the current to bemeasured.
 7. A device as claimed in claim 6, further comprisingrectifier means coupling the capacitance diode of the resonant circuitof the reflector means of said modulation device to said high voltageconductor thereby coupling said capacitance diode to a voltageproportional to the current to be measured.
 8. A device as claimed inclaim 7, further comprising saturation converting means energized by thecurrent to be measured for providing a constant auxiliary voltage fordetermining the working point of the capacitance diode of said resonantcircuit.
 9. A device as claimed in claim 1, wherein of the highfrequency oscillations transmitted by the transmitting means, thereflector means reflects that frequency which corresponds to theresonant frequency of said reflector means whereby the reflector meansreflects the frequency corresponding to a specific magnitude of thecurrent to be measured since the resonant frequency of the reflectormeans varies in accordance with the current to be measured.